表面化学Micelleformation

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1、MicelleformationWhentheconcentrationofsurfactantreachesacriticalconcentration,thehydrophobeofthesurfactantwillorganizetoformmicelle.Inthemicelle,thelipophilichydrocarbonchainsareorientatedtowardstheinteriorofthemicelle,leavingthehydrophilicgroupsoncontactwiththeaqueousmed

2、ium.Theconcentrationabovewhichmicelleformationbecomesappreciableistermedthecriticalmicelleconcentration(CMC).PropertiesofmicelleSeveralphysicalpropertiesofsurfactantsolutionabruptlychangeatCMC.ConcentrationMolarconductivitySurfacetensionOsmoticpressureTurbidityCMCMeasurem

3、entofCMCSurfacetensionmethodMeasurethesurfacetensionofthesolutionwithdifferentconcentrations;Plotthe-lnccurve.Extendthetwolineattheturningpoint.TheconcentrationatthecrosspointisCMC.CMCCharacteristicSimple,convenientValidforallofthesurfactantsSensitivityisindependentofsu

4、rfacetants,activitiesandtemperatureetc..ElectricalconductivityInthismethod,thevariationofelectricalconductivitywithsurfactantconcentrationisdetermined.OnlyavailableforionicsurfactantsolutionTheaccuracyisrelatedtotheCMCThesensitivityaffectsbyinorganicelectrolyteDyesolubili

5、zationAddingdyeintowaterandthendroppingthesurfactantsolutiontocolorchange,OraddingdyeintothesolutionwhichconcentrationislargerthanCMCandthendilutingthesolutiontothecolorchange.CMCistheconcentrationwhenthecolorchanges.Simple,convenientTheaccuracyisaffectedbytheamountofdyeT

6、urbiditymethodProbecompoundisaddedintothesurfactantsolution.WhentheconcentrationisbelowCMC,itiscloudy.WhentheconcentrationisaboveCMC,thesolutionisclear.CMCistheconcentrationwhentheabruptchangeoccures.Simple,convenientTheaccuracyisaffectedbytheamountofcompoundLightscatteri

7、ngCMCisdeterminedthroughmeasurementthevariationofintensityoflightscatteringwiththeconcentration.Validforallofthesurfactantsolutions.FactorsaffectingcriticalmicelleconcentrationsStructureofthesurfactantWhenthehydrophobeissame,theCMCofionicsurfactantislargerthannon-ionic.In

8、creasingthehydrophobicpartofthesurfactantfavoursmicelleformation.TheCMCofionicsurfactantsisappro